linux-kernel - Re: [PATCH] debugfs: add helper function to create device related seq

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Date:	Sat, 11 Oct 2014 18:09:47 +0200
From:	Arend van Spriel <arend@...adcom.com>
To:	Arend van Spriel <arend@...adcom.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] debugfs: add helper function to create device related
 seq_file

On 10/11/14 18:01, Arend van Spriel wrote:
> This patch adds a helper function that simplifies adding a
> sequence file for device drivers. The calling device driver
> needs to provide a read function and a device pointer. The
> field struct seq_file::private will reference the device
> pointer upon call to the read function so the driver can
> obtain his data from it and do its seq_printf() calls.

Maybe should have made this RFC first. Anyways, it is intended for 3.19, 
although I don't mind if it would end up in 3.18 :-p

Regards,
Arend

> Signed-off-by: Arend van Spriel<arend@...adcom.com>
> ---
>   fs/debugfs/file.c       | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
>   include/linux/debugfs.h | 16 ++++++++++++++-
>   2 files changed, 69 insertions(+), 1 deletion(-)
>
> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> index 76c08c2..088b3fc 100644
> --- a/fs/debugfs/file.c
> +++ b/fs/debugfs/file.c
> @@ -22,6 +22,7 @@
>   #include<linux/io.h>
>   #include<linux/slab.h>
>   #include<linux/atomic.h>
> +#include<linux/device.h>
>
>   static ssize_t default_read_file(struct file *file, char __user *buf,
>   				 size_t count, loff_t *ppos)
> @@ -761,3 +762,56 @@ struct dentry *debugfs_create_regset32(const char *name, umode_t mode,
>   EXPORT_SYMBOL_GPL(debugfs_create_regset32);
>
>   #endif /* CONFIG_HAS_IOMEM */
> +
> +struct debugfs_devm_entry {
> +	int (*read)(struct seq_file *seq, void *data);
> +	struct device *dev;
> +};
> +
> +static int debugfs_devm_entry_open(struct inode *inode, struct file *f)
> +{
> +	struct debugfs_devm_entry *entry = inode->i_private;
> +
> +	return single_open(f, entry->read, entry->dev);
> +}
> +
> +static const struct file_operations debugfs_devm_entry_ops = {
> +	.owner = THIS_MODULE,
> +	.open = debugfs_devm_entry_open,
> +	.release = single_release,
> +	.read = seq_read,
> +	.llseek = seq_lseek
> +};
> +
> +/**
> + * debugfs_create_devm_seqfile - create a debugfs file that is bound to device.
> + *
> + * @dev: device related to this debugfs file.
> + * @name: name of the debugfs file.
> + * @parent: a pointer to the parent dentry for this file.  This should be a
> + *	directory dentry if set.  If this parameter is %NULL, then the
> + *	file will be created in the root of the debugfs filesystem.
> + * @read_fn: function pointer called to print the seq_file content.
> + */
> +struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
> +					   struct dentry *parent,
> +					   int (*read_fn)(struct seq_file *s,
> +					   	   	  void *data))
> +{
> +	struct debugfs_devm_entry *entry;
> +
> +	if (IS_ERR(parent))
> +		return ERR_PTR(-ENOENT);
> +
> +	entry = devm_kzalloc(dev, sizeof(*entry), GFP_KERNEL);
> +	if (!entry)
> +		return ERR_PTR(-ENOMEM);
> +
> +	entry->read = read_fn;
> +	entry->dev = dev;
> +
> +	return debugfs_create_file(name, S_IRUGO, parent, entry,
> +				&debugfs_devm_entry_ops);
> +}
> +EXPORT_SYMBOL_GPL(debugfs_create_devm_seqfile);
> +
> diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
> index 4d0b4d1..f8c0db4 100644
> --- a/include/linux/debugfs.h
> +++ b/include/linux/debugfs.h
> @@ -99,13 +99,18 @@ struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
>   					struct dentry *parent,
>   					u32 *array, u32 elements);
>
> +struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
> +					   struct dentry *parent,
> +					   int (*read_fn)(struct seq_file *s,
> +					   	   	  void *data));
> +
>   bool debugfs_initialized(void);
>
>   #else
>
>   #include<linux/err.h>
>
> -/*
> +/*
>    * We do not return NULL from these functions if CONFIG_DEBUG_FS is not enabled
>    * so users have a chance to detect if there was a real error or not.  We don't
>    * want to duplicate the design decision mistakes of procfs and devfs again.
> @@ -251,6 +256,15 @@ static inline struct dentry *debugfs_create_u32_array(const char *name, umode_t
>   	return ERR_PTR(-ENODEV);
>   }
>
> +static inline struct dentry *debugfs_create_devm_seqfile(struct device *dev,
> +							 const char *name,
> +							 struct dentry *parent,
> +					   int (*read_fn)(struct seq_file *s,
> +					   	   	  void *data))
> +{
> +	return ERR_PTR(-ENODEV);
> +}
> +
>   #endif
>
>   #endif

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